Tractor safety switch



Oct. 25, 1955 J. L. RUTLEDGE 2,721,912

TRACTOR SAFETY SWITCH Filed Aug. 14, 1953 INVENTOR. a/OH/V/E 4.. 20715005,

United States Patent TRACTOR SAFETY SWITCH Johnie L. Rutledge, Monticello, Miss.

Application August 14, 1953, Serial No. 374,236

4 Claims. (Cl. ZOO-61.47)

This invention relates to an improved safety switch for a tractor and the like for cutting out the tractor motor whenever a predetermined unsafe tilt of the tractor occurs, and the primary object of the invention is to provide a more efficient and reliable device of this kind, which is of simple design, composed of a minimum number of parts, and can be produced in a rugged and serviceable form at relatively low cost.

Other important objects and advantageous features of the invention will be apparent from the following description and the accompanying drawings, wherein, for purposes of illustration only, a specific embodiment of the invention is set forth in detail.

In the drawing:

Figure l is a side elevational view showing a farm tractor equipped with a safety switch in accordance with the present invention, a backwardly tilted position of the tractor being shown in dotted lines;

Figure 2 is a right hand end elevation of Figure 3; and switch shown in Figures 1 and 3; and

Figure 3 is a vertical longitudinal section taken on the line 3-3 of Figure 2.

Referring in detail to the drawing, wherein like numerals designate like parts throughout the several views, the numeral 5 generally designates a conventional form of farm tractor having an engine crankcase structure 6 upon which is fixedly mounted, by means of a bracket 7, a mercury safety switch, generally designated 9, in accordance with the present invention. It will be understood that the switch 9 can be mounted on any other suitable place on a tractor.

The switch 9 comprises a preferably metal plate-like base 16 and an inverted U-shaped yoke or bracket 11, having vertical legs 12 and 13 fixedly secured at their lower ends to the base 10, the legs 12 and 13 being preferably perpendicular to the base and the bight portion 14 parallel to the base 10.

A preferably L-shaped rigid bracket 15 rises from the base 19 between the legs 12 and 13 and has a foot portion 16 fixed by suitable means to the base at a point about midway between the legs 12 and 13 and intermediate the side edges 17 and 18 of the base, and an upright or standard portion 19 arranged perpendicular to the base it The standard portion 19 is somewhat nearer to the leg 13 than to the leg 12 and rises about half of the height of the legs and has a free upper end 20.

A rock shaft or axle 21 is secured to the upper end of the standard portion 19 and projects laterally therefrom at one side of the standard portion 19. The switch 9 further comprises a tiltable body 22 which is tiltably mounted on the rock shaft or axle 21.

The tiltable body 22 comprises a normally elevated, preferably metal mercury tube 23, a normally depressed preferably glass mercury tube 24, the tubes 23 and 24 being preferably of the same capacity and dimensions, a substantially smaller diameter metal transfer tube 25 connecting the mercury tubes, and a relatively small diameter air venting tube 26 connecting the mercury tubes.

2,721,912 Patented Oct. 25, 1955 The mercury tubes 23 and 24 are axially spaced from each other at a distance of about the length of one of the mercury tubes and the transfer tube 25 is secured to the mercury tubes and opens into their axially inward ends at the lower sides of the mercury tubes. The air venting tube 26 is located above the mercury tubes 23 and 24 and has downturned ends 27 and 28 opening through the top walls of the mercury tubes near their axially inward ends.

Midway between the ends of the transfer tube 25, which is preferably metal, there is fixed on the upper side of the transfer tube a preferably metal hub 29, through which the axle or rock shaft 21 extends, whereby the body 22 is supported for tilting or rocking from the normal forwardly down-tilted position shown in Figure 3, to a rearwardly down-tilted position.

In the normal forwardly down-tilted position, which is maintained by the weight of a body of mercury 30 present in the mercury tube 24, when the tractor 5 is in a horizontal position or has not been rearwardly tilted beyond a predetermined safe angle, the mercury tube 24 rests upon a rest 31 which is in the form of an L-shaped bracket having a standard portion 32 engaged against the laterally inward side of the leg 13 of the yoke 11 and a horizontal foot portion 33 upon which the mercury tube 24 rests. The yoke leg 13 has a vertical slot 34 through which extends a bolt 35 which traverses the standard portion 32. The bolt 35 has a head 36 hearing against the laterally outward side of the yoke leg 13, and a clamping nut 37 hearing against the exposed side of the standard portion 32, the bolt 35 being capable of being loosened and the rest 31 adjusted downwardly with respect to a zero point 38 on a scale 39 marked on the laterally outward side 40 of the yoke leg 13, as ShOWn in Figure 2, and the bolt retightened to secure the adjustment. In this way the safety angle with respect to the horizontal, at which the tiltable body 22 will tilt rearwardly and downwardly from its normal position, upon upward and forward tilting of the tractor, can be predetermined and changed when desired, so as to predetermine the cutting out or shutting off of the engine 58 of the tractor 5.

Fixed on the rearward end of the rear mercury tube 23 of the tiltable body 22 is a spring contactor 42 which includes a shank portion 43 secured to the axially outward end of the metal mercury tube 23 and a vertical finger 44 depending from the outer end of the shank. The contactor 42 has electrical connection with the base 10 through the metal mercury tube 23, the transfer tube 25, the axle 21, and the bracket 15. A grounding wire 45 is connected by a binding post 46 preferably with the leg 12 of the yoke 11, which in turn is electrically connected with the base 10.

Mounted on the yoke leg 12 is an insulated contact 47 which includes a horizontally elongated di-electric block 48 extending laterally inwardly from the laterally inward side of the yoke leg 12, with a squared end 49 bearing against the leg 12 and a forwardly and downwardly angulated free end 5t) located in the path of downward tilt of the contactor 42 as the tiltable body 22 is tilted downwardly and reaiwardly from its normal position.

Fixed on the angulated end 50 of the di-electric block 48 is a conductive plate 51 which has an upward extension 52 to which is secured at 52 an end of an insulated wire 53 which leads through a grommet 54 on the yoke leg 12.

The block 48 is adjustably mounted on the yoke leg 12 by means of a screw 55 which is threaded through the leg 12 and into the squared end of the block and has thereon a lock nut 56 arranged to bear against the laterally outward side of the leg 12. The block 48 is thereby 3 adjustable lengthwise to place the contact plate 51 for proper engagement by the contactor 42.

In installing the safety switch 9, the adjustment of the position of the rest 31 is made with the tractor 5 level. The grounding wire 45, is connected to a suitable grounded part of .the tractor 5, and the insulated magnetorod wire .53 is connected to the ignition coil 57 of the tractor .engine 5.8. With this arrangement, Whenever the tractor 5 tilts upwardly and forwardly at an angle greater than the predetermined safety angle, the tiltable body 22 will swing out of its normal position and engage the contactor 42 With the contact plate 51 and thereby short out the ignition system of the engine 58 and stop the engine. The frictional engagement of the contactor 42 with the contact plate 51 and the Weight of the mercury in the tube 23 are suflicient to hold them in contact, so that restarting of the engine 58 while the tractor 5 is in an unsafe tilted position will be prevented. It will be obvious that the above described safety switch could also be mounted crosswise of a tractor, so as to operate whenever unsafe sidewise tilting of the tractor occured. A dust-proof and moisture-proof casing 59 is preferably engaged over the yoke 11 to protectively enclose the working parts.

What is claimed is:

1. In a tractor safety switch, a conductive base, a yoke fixed on the base, said yoke having a pair of legs, at least one of said legs being conductive and electrically connected to said base, an insulated contact fixed on said con- .ductive leg, an insulated wire leading from said contact, a grounding wire connected to said conductive leg, a bracket secured to said base at a point intermediate said legs, a tiltable body mounted on said bracket, said tiltable body comprising a pair of mercury tubes in axially spaced relation, one of said mercury tubes being conductive, a conductive transfer tube extending between and fixed to the axially inward ends of the mercury tubes and being in communication with the mercury tubes, a hub intermediate the ends of said transfer tube, an axle on said bracket traversing said hub whereby said tiltable body can tilt from a first normal position to a second operative position in response to tilting of the tractor, a contactor on and electrically connected to said conductive mercury tube, said contactor being arranged to electrically engage said contact only in operative position of the tiltable body.

2. In a tractor safety switch, a conductive base, a yoke fixed on the base, said yoke having a pair of legs, at least one of said legs being conductive and electrically connected to said base, an insulated contact fixed on said conductive leg, an insulated wire leading from said contact, a grounding wire connected to said conductive leg, a bracket secured to said base at a point intermediate said legs, a tiltable body mounted on said bracket, said tiltable body comprising a pair of mercury tubes in axially spaced relation, one of said mercury tubes being conductive, a

conductive transfer tube extending between and fixed to the axially inward ends of the mercury tubes and being in communication with the mercury tubes, a hub intermediate the ends of said transfer tube, an axle on said bracket traversing said hub whereby said tiltable body can tilt from a first normal position to a second operative position in response to tilting of the tractor, a contactor on and electrically connected to said conductive mercury tube, said contactor being arranged to electrically engage said contact only in operative position of the tiltable body, rest on the other leg of the yoke upon which the other mercury tube is arranged to rest in the normal position of said tiltable body, and means securing said rest to said other yoke leg and providing for adjustment of said rest along said other yoke leg so as to predetermine the angle of tilt of the base and tractor at which said tiltable body will tilt from its normal position to its operative position.

3. In a tractor safety switch, .a base, an insulated contact on said base, a leg on said base spaced along the base from said contact, a bracket secured to the base between said contact and said leg, a tiltable body pivoted intermediate its ends on said bracket, a contactor on one end of said tiltable body for engagement with said contact in an operative position of said tiltable body responsive to unsafe tilting of the tractor, said tiltable body comprising a pair of axially aligned mercury tubes and a body of mercury in one of the mercury tubes, means for transferring said body of mercury between the tubes as said tiltable body is pivoted from a normal position to said operative position and from said operative position to said normal position whereby said tiltable body is overbalanced in either of said positions, and a rest on said leg upon which the end of the mercury tube remote from said contactor is arranged to rest when overbalanced in the normal position of the tiltable body, said rest being adjustable along said leg to predetermine the normal position of said tiltable body.

4. In a tractor safety switch, a conductive base, an inverted U-shaped conductor yoke secured to said base, said yoke having legs, means on said yoke for connecting thereto one side of an electrical circuit, an insulated contact mounted on said one leg for connection to the other side of the circuit, a bracket mounted on said base between said legs and electrically connected to said yoke, a freely tiltable mercury tube pivoted intermediate its ends on said bracket, tube having an intermediate conductor position, a contactor on one end of said tube arranged to engage said contact in a first tilted position of said body, a rest projecting from the other leg of the yoke upon which the other end of said tube is arranged to rest in a second tilted position of said tube, said tube containing a quantity of mercury, and conductive means on said one end of the tube, said conductive means being connected to said contactor and being exposed within said one end of the mercury tube for contact of mercury therewith in said first tilted position of said body.

References Cited in the file of this patent UNITED STATES PATENTS 

